Commercial products available for correcting typewritten, handwritten, and photocopy markings on papers are formulated using halogenated solvents and/or hydrocarbons to obtain the desired performance properties of the film. A typical correction fluid composition contains an opacifying agent such as titanium dioxide, a binder, a dispersing agent and a solvent or a mixture of solvents. The binder is generally a film forming polymer soluble in the selected solvent medium which also binds pigments to paper substrate. The solvent acts as a carrier for the ingredients in the correction fluid.
Halogenated hydrocarbon solvents are generally the solvent of choice in correction fluids because halogenated hydrocarbons dry rapidly without interacting with typewritten markings to cause unacceptable bleeding. Halogenated hydrocarbons also have the advantage of dissolving the polymeric-film forming material which provides a flexible and durable film. The use of halogenated hydrocarbon solvents, however, present several health and environmental problems. Halogenated and nonhalogenated hydrocarbon vapors which are generated during drying of the correction fluid are harmful to the health of workers and users. Moreover, halogenated hydrocarbon vapors adversely effect the environment by depleting stratospheric ozone.
U.S. Pat. Nos. 5,199,976 and 5,256,191, and U.K. Pat. App. No. GB 2,058,110 disclose correction fluids which either are free from material that migrates to the stratosphere or, in case it contains such a material, the material does not cause appreciable effect on reducing ozone concentration. U.S. Pat. No. 5,199,976 discloses a correction fluid containing a hydrocarbon solvent, a vinyl toluene-butadiene copolymer as the polymeric-film forming material, a dispersing agent and an opacifying pigment. Such hydrocarbon solvents, however, release volatile organic compounds into the air, and thus, present a health risk to workers and users.
U.S. Pat. No. 5,256,191 discloses a substantially non-toxic correction fluid which contains an opacifying pigment dispersed in a solution of a nonhalogenated solvent, a siloxane and an acrylic resin having a weight average molecular weight of 50,000 to 500,000. The solvents used include siloxane(s) and polar solvents such as ethyl alcohol, isopropanol, methyl ethylketone and ethyl acetate. Such polar solvents, however, release volatile organic compounds into the air, and thus, present a health risk to workers and users. Moreover, the use of high molecular weight acrylic resins results in solutions which are too viscous to add enough opacifying pigment to provide the necessary hiding power.
U.K. Pat. App. No. GB 2,058,110A discloses an aqueous correction fluid containing a stable emulsion of a water-dispersed, water-insoluble acrylic resin as a binder for the masking pigment. While, the correction fluid forms smooth, highly opaque, and flexible masking coatings, it has an unacceptable drying time due to a water content in the range of 25 to 50 weight percent.
Accordingly, what is needed is a correction fluid which does not contain halogenated solvents or hydrocarbon solvents, but which can be used to correct all types of markings (e.g. typewritten, handwritten, photocopied and laser-jet printed) formed with waterborne or solventborne inks.